Louise Yamada believes the market downturn is not securely in the past.
According to the Wall Street technician, a retest of the December low is possible.
"It's too soon to know from our perspective whether it's a rally in a bear market or an extension of the 2009 bull because rallies can retrace through to the high and still fail," she said Thursday on CNBC's "Futures Now."
Yamada, who runs Louise Yamada Technical Research Advisors, acknowledges that 2800 is a key level on the S&P 500. But she contends getting through that threshold doesn't ensure stocks are out of the woods.
"[You] still have to look at the characteristic of the market as it approaches the old high because sometimes it can roll over once again," she said.
She uses 2015 as an example of a rally that failed to hold.
"If you look back at the 2015 chart, there it went through it considerably three times and couldn't progress much beyond it," said Yamada. "So, I think we're due for a little testing."
The S&P 500 hit its all-time high of 2940 on Sept. 21, 2018. By December, the index was getting battered by a deep correction — with the biggest plunge happening on Christmas Eve.
Since the December low, the S&P 500 has surged 18 percent and closed Friday at 2775.60.
"The best case would be for the markets to go sideways here between 2600 and 2800 which would be constructive and allow for a period of repair which thereafter a push through 2800 could be more meaningful," Yamada said.